Ingot mold



Patented May 26, 193.1

PATENT OFFICE EMIL GATHMANN, OF BALTIMORE, MARYLAND IN GOT MOLD Application filed September l5, 1926. Serial No. 135,586.

This invention rela-tes to metallic ingot molds of the class having vertical in got-formlng chambers and particularly to molds which are open at top and bottom with walls lrelatively thick in theirA lower portion and gradually decreasing in thickness upwards. In pouring or teeming such molds the stream of highly heated molten metal. in the. first part of the pouring, strikes the mold chamber Walls in the lower portion of t-he mold chamber with great force and heretofore has often cut into the mold walls and suddenly heated them, thereby setting up strains or stresses which cause cracks vor recesses to be formed lwhich often'seriously impairthe life or efficiency of the mold and make the strip ping operation difficult.

The object of my present invention is to prevent theforma'tion of such cracks or recesses and to thus lengthen the life'of the mold and to facilitatethe stripping operation. Broadly stated,my`invent'ion consists in rendering harder and more heat resisting the lower portion'of the'inner walls of the mold chamber than the mold .walls above Ysuch lower portion so that-said lower walls may receive the impact ofthe stream of molten metal without being injured while the upper walls reta-in the desirable characteristics of the cast iron usually employed in Thel accompanying vdrawings are largely diagrammatic but sufficiently illustrate the bes/t ways now known t0 me of carrying out my invention.

Figure 1 shows a. vertical section of an ingot mold of well known construction with my improvements applied.

Figure 2 is a sectional view of the. lower portion of the. mold, the section being taken on the line 2-2 ofFigure 1.

Figure 8 shows a vertical section of an ingot mold provided with a modified form of my invention.

Figure 4 is a sectional View of the lower portion of the mold. the section being taken on the. line 4 4 of Figure 3.

Figure 5 is a. View similar to Figure 4. the section being taken on the line 5-5 of Fig- The mold shown in Figure- 1 has an ingot. forming chamber A larger in diameter or cross section in its upper than in its lower portion, the chamber gradually or progressively increasingr in width from bottonrup- Wards. The mold is open' at top and at bot tom and the lower portion ofthe mold cham`v ber is necked-in by inner mold walls a. having a concave-convex contour of the kind shown` described and claimed in my U. S. Patent No. 1.188.751 of June 27, 1916. 'lhe bottom opening B of the. mold may be. closed by a. plug C in the usual way or by other .suitablemeans. The walls of the mold are thicker in their lower portion than in their upper part for a purpose now well understood and the mold, for the. most part, is made of cast iron of the usual kind. Generally such molds are made of an open grade. of Bessemer cast iron containing: approximately the following ingredients: silicon 1.25; manganese 0.80; sulphur (under) 0.06; phosA phorous (under)' 0.20; total carbon 3.75.

vThe contained graphit-ic carbon usually runs `(2,200" F. t-o 2.300C is relatively low compared with thel temperature of steel while being cast. which varies from 26000 F. to 2900n F. and at times is even higher. As a highly heated stream of molten metal enters a mold chamber and strikes against the bottom or lower walls ol' the chamber. which at. first are relatively cool. it often cuts, erodes or even melts the mold walls with which it comes in Contact` or so heats said walls as to cause such strains or stresses to be produced as will cause. cracks or recesses therein. This has often so changed the contour of the lower portion of the mold chamber as to render the mold inefficient and this has often occurred long before the upper portion of the mold has been seriously impaired. This wearing away of the mold Walls is primarily due to cumulative strains produced b y continued expansion and contraction of the mold walls caused by temperature changes.

If an ingot mold were made entirely of steel, which has a high melting point and hence greater heat resisting qualities than cast iron, the mold Walls would be more resistant to the cutting and erosive action of the liquid steel poured into the mold, but steel walls arc not suitable for making ingot molds because such steel walls do not so readily expand a-nd contract as do mold walls made of cast iron and therefore they would warp to such an extent as to prevent the removal of the ingot from the mold. Furthermore, the cost of steel molds would be so milch greater than cast iron molds that steel could not be used economically. I therefore make the mold principally of cast iron as .heretofore andV so form or so treat the lower portion of the inner mold Walls as to render them harder and more heat resisting than the remaining walls. This may be accomplished in various ways. One Way is to form the lower inner mold walls of an alloy of iron with a substance havingr a high melting point, such as vanadium, molybdenum tungsten, chrome or other such metal. Vanadium for instance, has a melting temperature of approximately 3100o F., which is considerably higher than the temperature of steel when teemed into a mold.

It will be understood that the lower portion only of the mold walls should be given the heat resisting qualities above mentioned in order that the upper part of the walls shall have the desirable characteristics of expanding and contracting without cracking, which as before stated, is inherent in gray iron of the kind generally employed in making ingot molds.

Ingot molds of the kind shown are usually lcast in sand fiasks, bottom end uppermost.

In preparing the flask to cast molds of the kind shown in Figures 1 and 2 with my improvements applied, the core of the sand mold is formed in the usual Way and a. block of high heat resisting material is placed on lthe core at its upper end so that the molten metal will surround the-block when it rises in the ask and will be firmly united there- With when the metal cools and solidifies. The block thus constitutes the upper end of the core during the casting operation. Preferably the block D of high heat resisting material is of the form shown in Figure 1, being tapered as shown and having a serrated upper edge whereby it may be lirmly locked to the main mold walls. In the construction shown in Figure 1, the bottom of the mold chamber is formed in lthe block D and the necked-in portion of the mold chamber is formed in this block. The block may be formed of an iron alloy of the kind previously described and is, of course, made separately and placed in the sand mold in the manner above explained. The block D in the completed mold is not separable from the mold; it is a permanent part thereof.

The mold shown in Figures 3, 4 and 5 has the lower walls of the cast-iron mold treated to render these walls highly heat resisting. To accomplish this result, the loam or foundry sand composing that portion of the core for forming the lower part of the mold chamber is impregnated and coated with a flourlike metallic dust such as powdered vanadium, molybdenum, chrome and the like made into a paste with molasses and water or other such binder. When the molten metal rises in the sand fiask and surrounds the treated core or a part thereof, this treated part of the core adheres to or is absorbed by the cast metal. In this way a lining or a casing of high heat resisting iron or iron alloy is provided in the' lower portion of the mold chamber. In Figures 3, 4 and 5 the lining or treated portion of the mold wall is indicated at E. The high heat resisting material should not extend to any 'considerable extent above the necked-in part of the mold chamber as the desired qualities of ready expansion and contraction of the mold would be impaired if any considerable portion of the walls above the necked-in portion were materially changed. While I have shown in the drawings two practical ways of embodying my invention in ingot molds, it will be understood that the details illustrated and described may be varied without departing from the novel features of my invention.

A cast iron ingot mold made in accordance with my invention has a portion of the matrix side wall of close grained metal comprising double carbides of iron and another metal and where chromium is employed, a portion of the mold wall is impregnated'with chro mium carbide.

The forming molds in which the ingot molds are cast are of usual construction exceptA as modified in the manner above described. In my U. S. Patent No. 1,719,544 of July 2, 1929, I have claimed the method herein described of forming ingot molds.

I claim as my invention:

1. An ingot mold having a vertical ingotforming chamber, the inner chamber side Walls of which at the lower portion of the mold are formed of an alloyed metal more heat-resisting than the remaining mold walls to the cutting action of liquid steel.

2. A cast iron mold having a vertical ingot-forming chamber the lower inner walls of which are provided with a heat-resisting alloyed portion.

3. As an article of manufacture, a cast iron ingot mold member having a portion of the matrix side wall of close grained metal cornprisingz double carbides of iron and another mttai.

4. An nrtivlv of nnmnfnvture comprising a rust iron ingot mold nwlnber having: a porn tion of the wall lhvreof inprognatvd with chromium carbide.

5. A rast iron mold having a vertical ingot forming' chamber. open at. the bottom, in Combination with a block of heat resisting Inaterinl inwrted in the lower portion of tho mold and which is formed of :1n alloyed metal more. heut resisting than the renmining;r mold fails to the cuttingl action of liquid steel.

Tn testimony whereof, I have hereunto subscribed my name.

EMIL GATHMANN. 

